FRIDAY, Aug. 24 (HealthDay News) -- Some childhood cancer survivors who underwent radiation therapy may have an increased risk of developing diabetes later in life, according to a new study that is the first to make a link between radiation and diabetes.

Researchers looked at more than 2,500 people in France and the United Kingdom who had been treated for cancer in childhood between 1946 and 1985, and survived for at least 20 years after undergoing treatment.

At age 45, diabetes had been diagnosed in 6.6 percent of the patients who had undergone radiation therapy and 2.3 percent of those who did not have radiation therapy, the study found.

The researchers determined how the radiation would have been applied to patients and found that the likelihood of being diagnosed with diabetes was much higher when the tail of the pancreas had been exposed to radiation. However, radiation exposure to other parts of the pancreas did not affect diabetes risk.

This difference may be due to the fact that the tail of the pancreas contains a type of cell involved in insulin production, the researchers suggested.

The study also found that people who received higher doses of radiation to the tail of the pancreas were nearly 13 times more likely to be diagnosed with diabetes within 20 years than those who did not receive radiation therapy.

Type of cancer also affected diabetes risk. By age 45, diabetes was diagnosed in nearly 15 percent of patients who had been treated for kidney cancer, compared with an average of 3 percent for other types of cancer included in the study, such as lymphoma.

Radiation therapy for kidney cancer often focuses in the abdominal area, which increases the chance that the tail of the pancreas will be exposed to radiation, the researchers noted.

The study was published online Aug. 23 in The Lancet Oncology.

"The pancreas needs to be regarded as a critical organ when planning radiation therapy, particularly in children. Until now, the pancreas was one of the few organs not considered at risk of normal tissue complication in the French and the U.K. national guidelines for cancer radiation therapy," Dr. Florent de Vathaire of the Centre for Epidemiology and Public Health of the National Institute for Health and Medical Research, in France, said in a journal news release.

"Our findings indicate that the pancreas is an organ at risk during radiation therapy and has to be contoured when planning treatment, to ensure a radiation dose of as low as possible," de Vathaire concluded.

While the study uncovered an association between radiation therapy in childhood and diabetes later in life, it did not prove a cause-and-effect relationship.

More information

The U.S. National Cancer Institute has more about the late effects of treatment for childhood cancer.